Spectrometer and spectrally separating method

ABSTRACT

A light from a light source is transmitted through a sample cell and is made incident into a spectroscopic portion. The spectroscopic portion comprises interference filters which transmit light components different in wavelengths and photodiodes corresponding to the respective interference filters. Dielectric films to compose an interference filter have relatively satisfactory features to reflect a light component of wavelengths other than a light component of a wavelength to be transmitted. At each interference filter, an incident light is split into a light component to be transmitted and a light component to be reflected. By making the reflected light component into an incident light into a following-order interference filter, light components of nine wavelength types are detected.

TECHNICAL FIELD

This invention relates to a spectroscopic instrument and a spectroscopicmethod to be used in, for example, a blood test.

BACKGROUND ART

A spectroscopic instrument is an instrument for measuring absorbency ofa testing sample by irradiating light from a light source onto the testsample and changing intensity of the light transmitted through orreflected from the test sample to an electric signal, and has beenapplied to various fields. When a spectroscopic instrument is appliedto, for example, a color measurement or a blood test, out of lighttransmitted through a test sample, absorbency of a plurality of lightcomponents different in wavelengths, namely, each of the multiplewavelengths is measured. Such spectroscopic instruments include a rotaryplate-system spectroscopic instrument as disclosed in JapaneseUnexamined Patent Publication No. Sho-59-131124, for example. In thisspectroscopic instrument, by mechanically rotating a rotary plate sothat a filter which transmits a light component of a wavelength to bedetected is located in an optical path, detection of multiplewavelengths is enabled.

However, since the rotary plate-system spectroscopic instrument selectsa filter by mechanically rotating the rotary plate, it takes time todetect multiple wavelengths. Although a quick examination of multiplesamples and multiple items is demanded in a blood test, the rotaryplate-system instrument cannot satisfy this demand.

Instruments to satisfy this demand include half mirror-systemspectroscopic instruments as disclosed in Japanese Unexamined PatentPublication No. Hei-11-6766 and Japanese Unexamined Patent PublicationNo. Sho-59-170734, for example. These spectroscopic instruments have astructure to detect multiple wavelengths by a plurality of half mirrorsand a plurality of light-receiving elements. The half mirror-systemspectroscopic instrument detects multiple wavelengths by splitting, atrespective half mirrors, an incident light into a transmitted light anda reflected light and using the transmitted light as an incident lightof a half mirror positioned in the next order. Therefore, compared tothe above-described rotary plate-system spectroscopic instrument thatdetects multiple wavelengths by mechanically selecting a wavelength,multiple wavelengths can be speedily detected.

SUMMARY OF THE INVENTION

However, according to a half mirror-system spectroscopic instrument, alight flux is split into one second by each half mirror. Accordingly,the S/N ratio declines at light-receiving elements positioned in thelatter orders since an incident light weakens considerably, wherebydetecting efficiency, which is a light component detecting sensitivity,is deteriorated. For example, if eight half mirrors are provided todetect nine wavelength types, light intensity of light transmittedthrough the eighth half mirror becomes (½)⁸= 1/256 compared to theinitial intensity, and detecting efficiency of a light component of thatwavelength is considerably deteriorated. In order to cope therewith, theamount of light from the light source must be increased, however, thisresults in an increase in power consumption.

The present invention has been made to solve such conventional problemsand to provide a spectroscopic instrument and a spectroscopic methodwhich can detect a plurality of light components different inwavelengths at a high detecting efficiency and at a high speed.

A spectroscopic instrument according to the present invention is aspectroscopic instrument for detecting a plurality of light componentsdifferent in wavelengths, comprising: a plurality of interferencefilters which are respectively different in wavelengths of lightcomponents to be transmitted therethrough and to which a light from alight source is transmitted in order; and a plurality of photodetectingmeans corresponding to each of the plurality of interference filters,for detecting a light component transmitted through the correspondinginterference filter, wherein each of the plurality of interferencefilters splits an incident light into a light component to be reflectedand a light component to be transmitted and makes the reflected lightcomponent into an incident light into an interference filter positionedin the next order, whereby the light from the light source istransmitted to the plurality of interference filters in order.

According to the spectroscopic instrument of the present invention, theplurality of interference filters split the irrespective incident lightsin to a light component to be reflected and a light component to betransmitted and make the reflected light component into an incidentlight into an interference filter positioned in the next order, wherebya light from the light source is transmitted to the plurality ofinterference filters in order, and light components transmitted throughthe respective interference filters are detected by the respective photodetecting means, where by multiple wavelengths are detected. Aninterference filter is composed of dielectric layers (dielectricmultilayered films), and a light component of a predetermined wavelengthis transmitted by an interference effect of the dielectric layers.According to the present inventor, it has been discovered that thesedielectric layers have relatively satisfactory features to reflect alight component of wavelengths other than a light component of awavelength transmitted through the interference filter. Accordingly,since an incident light of a relatively high intensity is made incidentinto interference filters positioned in the latter orders, as well, thedetecting efficiency can be improved.

In addition, according to the spectroscopic instrument of the presentinvention, an incident light into each interference filter is split intoa light component to be transmitted and a light component to bereflected, and the reflected light component is made into an incidentlight into an interference filter positioned in the next order. Sincethe spectroscopic instrument according to the present invention detectsmultiple wavelengths by not mechanically but optically selecting awavelength, high-speed detection of multiple wavelengths becomespossible.

A spectroscopic method according to the present invention is aspectroscopic method for detecting a plurality of light componentsdifferent in wavelengths, wherein at each of a plurality of interferencefilters respectively different in wavelengths of light components to betransmitted therethrough, an incident light into each interferencefilter is split into a light component to be reflected and a lightcomponent to be transmitted and the reflected light component is madeinto an incident light into an interference filter positioned in thenext order, whereby a light from a light source is transmitted to theplurality of interference filters in order so as to detect lightcomponents transmitted through the respective interference filters.

According to the spectroscopic method of the present invention, forreasons similar to those of the spectroscopic instruments according tothe present invention, it becomes possible to detect a plurality oflight components different in wavelengths at a high detecting efficiencyand at a high speed.

Moreover, a spectroscopic instrument according to the present inventioncomprises: a plurality of photodetectors arranged so that the light ismade incident in time series at the speed of light, and is characterizedin that the photodetectors each have a photoelectric transducer and aninterference filter fixed to the light incident side of thephotoelectric transducer, a transmitting wavelength and a reflectingwavelength band of the respective interference filters are different,and a transmitting wavelength of the interference filter of a latterorder is included in a reflecting wavelength band of the interferencefilter of a former order. Irrespective of the transmitting wavelength ofthe interference filter, a total reflection mirror having an aperturemay be provided on the light incident surface side thereof.

In addition, if the plurality of photodetectors are arranged in acircle, an air flow-in path into the inside of the circle becomesnarrow, therefore, an output fluctuation of the photodetectors caused byair undulations can be suppressed.

In addition, if an infrared cut filter is arranged on the near side ofthe photodetectors, generation of noise caused by infrared light can besuppressed, and if the inner surface of a cylindrical body to compose aphotodetector is black, noise caused by an internal reflection of thecylindrical body can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a spectroscopic instrument according tothe first embodiment of the present invention.

FIG. 2 is a diagram indicating a graph showing a relationship betweenthe wavelength and reflectance of an interference filter (transmissionwavelength: 340 nm, 415 nm, 450 nm) provided in the first embodiment.

FIG. 3 is a diagram indicating a graph showing a relationship betweenthe wavelength and reflectance of an interference filter (transmissionwavelength: 510 nm, 540 nm, 568 nm) provided in the first embodiment.

FIG. 4 is a diagram indicating a graph showing a relationship betweenthe wavelength and reflectance of an interference filter (transmissionwavelength: 600 nm, 690 nm, 800 nm) provided in the first embodiment.

FIG. 5 is a schematic view of a spectroscopic instrument according tothe second embodiment of the present invention.

FIG. 6 is a plan view of a spectroscopic instrument according to anotherembodiment.

FIG. 7 is a sectional view of a first photodetector D1 when a firstphotodetector D1 is cut along the optical axis of the firstphotodetector D1.

FIG. 8 is a sectional view of a first photodetector D1 when a totalreflection mirror-type first photodetector D1 is cut along the opticalaxis of the first photodetector D1.

FIG. 9 is a view of a photodetector D1 showing internal components of aphotodetector D1 in an exploded manner.

FIG. 10 is a view showing an example where, in the spectroscopicinstrument shown in FIG. 1, total-reflection mirror-type photodetectorsD1–D5 . . . have been applied.

FIG. 11 is an enlarged sectional view of the third photodetector D3shown in FIG. 10.

FIG. 12 is a view showing an example where, in the spectroscopicinstrument shown in FIG. 1, an infrared cut filter is applied.

FIG. 13 is a view showing an example where, in the spectroscopicinstrument shown in FIG. 1, an infrared cut filter is applied.

BEST MODE FOR CARRYING OUT THE INVENTION

A spectroscopic instrument according to a preferred embodiment of thepresent invention will be described by use of drawings.

FIG. 1 is a schematic view of a spectroscopic instrument according to afirst embodiment of the present invention. A spectroscopic instrument 1is for detecting light components of nine wavelength types, whichcomprises: a light source 3 including, for example, a 20W-iodide bulb,two lenses 5 and 7 for condensing light L emitted from the light source3; an aperture 9 through which light L transmitted through the lenses 5and 7 passes; a lens 11 for making light L transmitted through theaperture 9 and transmitted through a sample cell S in which a testsample (for example, blood) is contained into parallel light rays; and aspectroscopic portion 13 into which light L made into parallel lightrays by the lens 11 is made incident. These components to construct thespectroscopic instrument 1 are housed in a casing (cylindrical body) 15.

The lens 5, lens 7, and aperture 9 are held by a holding portion 17, andthe lens 5, the lens 7, and the aperture 9 are arranged in order alongthe optical path of the light L. Section dimensions of light L when thelight L is made incident into the sample cell S are defined by the lens5, lens 7, and aperture 9. This section is a section located at a 90degree-angle with respect to the traveling direction of the light L, andthe dimensions are 3 mm long×3 mm wide, for example.

An arrangement place of the sample cell S exists in an optical pathbetween the aperture 9 and lens 11. In a manner sandwiching thisarrangement place, slits 19 and 21 are arranged. In addition, a slit 23is located in an optical path between the lens 11 and spectroscopicportion 13.

Now, a structure of the spectroscopic portion 13 will be described indetail. The spectroscopic portion 13 comprises: nine interferencefilters 31–39; and nine photodiodes 41–49 which correspond to therespective interference filters 31–39 and detect light componentstransmitted through the corresponding interference filters 31–39. Thephotodiodes 41–49 are examples of photodetecting means. Photodiodeswhich can be used in the present embodiment include a Si photodiode, forexample.

The interference filters 31, 33, 35, 37, and 39 are arranged so thattheir respective incident surfaces are lined in one direction, and inthis condition, the interference filters are held by a holding portion25. The holding portion 25 is arranged so that a light L made incidentinto the spectroscopic portion 13 is made incident into the interferencefilter 31 at an appointed angle. To respective emitting surfaces of theinterference filters 31, 33, 35, 37, and 39, the photodiodes 41, 43, 45,47, and 49 are attached. Thus, the respective photodiodes detect lightcomponents transmitted through the corresponding interference filters.

Similarly, the interference filters 32, 34, 36, and 38 are also arrangedso that their respective incident surfaces are lined in one direction,and in this condition, the interference filters are held by a holdingportion 27. The holding portion 27 is arranged at a position not tointersect an optical path of light L after being made incident into thespectroscopic portion 13 before being made incident into theinterference filter 31 so that the interference filters held by theholding portion 27 are opposed to the interference filters held by theholding portion 25. To respective emitting surfaces of the interferencefilters 32, 34, 36, and 38, the photodiodes 42, 44, 46, and 48 areattached. Thus, the respective photodiodes detect light componentstransmitted through the corresponding interference filters. In thespectroscopic portion 13, provided is an electronic circuit(unillustrated) such as an amplifier for amplifying the light componentsdetected by the respective photodiodes 41–49. These components toconstruct the spectroscopic portion 13 are housed in a casing(cylindrical body) 29.

The interference filters 31–39 split respective incident lights into alight component to be reflected and a light component to be transmitted.By arranging the holding portions 25 and 27 as in the above, a reflectedlight component becomes an incident light into an interference filterpositioned in the next order, whereby light L from the light source 3 istransmitted in numerical order of the interference filters 31–39. Theinterference filters 31–39 have functions as band-pass filters, andlight components of wavelengths which the respective filters transmitare shown in Table 1.

TABLE 1 Interference filter 31 340 nm Interference filter 32 415 nmInterference filter 33 450 nm Interference filter 34 510 nm Interferencefilter 35 540 nm Interference filter 36 568 nm Interference filter 37600 nm Interference filter 38 690 nm Interference filter 39 800 nm

Herein, an interference filter is an optical filter which is provided bylayering multiple thin films having an appointed optical thicknessformed by vapor deposition or the like on a substrate and utilizesinterference that occurs inside thereof for transmitting or reflectinglight of only a specific wavelength band. In general, an interferencefilter is composed of multi-layered dielectric films (for example, SiO₂,SiN, or TiO₂). According to the present inventor, it has been discoveredthat dielectric films to compose an interference filter reflect a lightcomponent of wavelengths other than a light component of a wavelengththat the interference filter transmits at a relatively high percentage(for example, 80% or more). FIG. 2˜FIG. 4 are graphs showingrelationships between the wavelength and reflectance of an interferencefilter obtained through experiments by the present inventor. In therespective graphs, the horizontal axis represents wavelength [nm] of anincident light into the interference filter, and the vertical axisrepresents reflectance [%] of an incident light.

In FIG. 2, the solid line of the graph represents data from theinterference filter 31 (transmission wavelength: 340 nm), the dottedline represents data from the interference filter 32 (transmissionwavelength: 415 nm), and an alternate long and short dash linerepresents data from the interference filter 33 (transmissionwavelength: 450 nm). In FIG. 3, the solid line of the graph representsdata from the interference filter 34 (transmission wavelength: 510 nm),the dotted line represents data from the interference filter 35(transmission wavelength: 540 nm), and an alternate long and short dashline represents data from the interference filter 36 (transmissionwavelength: 568 nm).

In FIG. 4, the solid line of the graph represents data from theinterference filter 37 (transmission wavelength: 600 nm), the dottedline represents data from the interference filter 38 (transmissionwavelength: 690 nm), and an alternate long and short dash linerepresents data from the interference filter 39 (transmissionwavelength: 800 nm).

As can be understood from these graphs, the interference filters 31–39have a relatively high transmittance with respect to a light componentof wavelengths other than the light component of the wavelength to betransmitted.

The present embodiment utilizes the above-described feature of theinterference filters. Namely, by making a light component reflected byeach interference filter into an incident light into an interferencefilter in the next order, an incident light of a relatively highintensity is made incident into the interference filters positioned inthe latter orders, as well.

Operations of the spectroscopic instrument 1 will be described by use ofFIG. 1. Light L generated from the light source 3 passes, after sectiondimensions thereof are defined to an appointed value by the lenses 5 and7 and aperture 9, through the slit 19 and is made incident into thesample cell S. After being transmitted through the sample cell S, thelight Lpasses through the slit 21 and is made incident into the lens 11.The light L is made into parallel light rays by the lens 11 and is madeincident into the spectroscopic portion 13 via the slit 23.

The light L made incident into the spectroscopic portion 13 is firstmade incident into the incident surface of the interference filter 31and is split by the interference filter 31 into a light component to betransmitted and a light component R1 to be reflected. The lightcomponent to be transmitted is a light component mainly of a wavelength340 nm and is detected by the photodiode 41.

As described in the foregoing, the interference filters have a featureto reflect most of the light component other than a light component of awavelength to be transmitted. Therefore, the light component R1 to bereflected by the interference filter 31 contains a light component ofwavelengths to be transmitted through the interference filters 32–39 inthe latter orders with a high intensity. The transmitted light componentR1 is made incident into the incident surface of the interference filter32 and is split by the interference filter 32 into a light component tobe transmitted and a light component R2 to be reflected. The lightcomponent transmitted through the interference filter 32 is a lightcomponent mainly of a wavelength 415 nm, and this light component isdetected by the photodiode 42. For similar reasons to the abovedescription, the reflected light R2 contains a light component ofwavelengths to be transmitted through the interference filters 33–39 inthe latter order with a high intensity.

Subsequently, similarly, light components transmitted through theinterference filters 33–39 are detected by the photodiodes 43–49.Accordingly, light components of nine wavelength types can be detectedby the spectroscopic instrument 1. Examples of output values [nA] of thelight components detected by the photodiodes 41–49 are shown in Table 2.

TABLE 2 Output value Ratio to Output with a a single value single filterfilter Reference [nA] [nA] [%] [%] Interference filter 31 28.9 28.9 10050 (340 nm) Interference filter 32 164.3 249.1 66.0 25.0 (415 nm)Interference filter 33 127.7 562.8 22.7 12.50 (450 nm) Interferencefilter 34 805.6 1315.0 61.3 6.25 (510 nm) Interference filter 35 1856.12156.0 86.1 3.13 (540 nm) Interference filter 36 2055.0 2587.0 79.4 1.56(568 nm) Interference filter 37 1540.0 2105.0 73.2 0.78 (600 nm)Interference filter 38 4118.0 4774.0 86.3 0.39 (690 nm) Interferencefilter 39 3492.0 4051.0 86.2 0.20 (800 nm)

Herein, “output value with a single filter” is an output value from thephotodiode when light L made incident into the spectroscopic portion 13is directly made incident into the respective interference filters31–39. “Ratio to a single filter [%]” is a percentage of the outputvalue from the respective photodiodes 41–49 when the output value with asingle filter is provided as 100%. “Reference” is a ratio [%] to asingle filter when a half mirror of a transmittance 50% is used in placeof the interference filter.

According to the present embodiment, it can be understood that even thelight components transmitted through the interference filters positionedin the latter orders (for example, the interference filters 35–39) haverelatively great output values. This is obvious at a glance by acomparison between the “ratio to a single filter” and “reference.” Inthe present embodiment, even the interference filters positioned in thelatter orders have relatively great percentages of the “ratio to asingle filter.” This indicates that intensity of a light componentdetected by each photodiode is relatively high, therefore, even lightcomponents of wavelengths transmitted through the interference filterspositioned in the latter orders can be improved in detecting efficiency.On the other hand, the ratio to a single filter when a half mirror isused as shown by the “reference” is exponentially reduced. Consequently,it can be understood that since intensity of the light componentstransmitted through the interference filters positioned in the latterorders becomes significantly small, the detecting efficiency isconsiderably deteriorated.

Therefore, according to the present embodiment, since multiplewavelengths can be detected without increasing the amount of light fromthe light source 3, low power consumption can be realized. In addition,according to the present embodiment, since no special components toincrease detecting efficiency are required either, a small-sized andlow-cost spectroscopic instrument can be provided.

In addition, according to the present embodiment, an incident light intoeach interference filter is split into a light component to be reflectedand a light component to be transmitted, and the reflected lightcomponent is made into an incident light of an interference filterpositioned in the next order, whereby light components of ninewavelength types are detected. As such, in the present embodiment, sincemultiple wavelengths are detected by not mechanically but opticallyselecting a wavelength, multiple wavelengths can be speedily detected.In addition, since a structure is employed wherein a plurality ofinterference filters 31–39 are arranged so that the light L from thelight source 3 is transmitted in order, multiple wavelengths can bedetected with a simple structure.

According to the present embodiment having the above effects, it becomespossible to utilize the spectroscopic instrument for a test of multiplesamples and multiple items such as, for example, a blood test.

Now, a spectroscopic instrument according to a second embodiment of thepresent invention will be described. FIG. 5 is a schematic view of aspectroscopic instrument 2 according to the second embodiment. In FIG.5, identical symbols are used for components equivalent to those of thespectroscopic instrument 1 shown in FIG. 1, whereby description thereofwill be omitted.

The spectroscopic instrument 2 detects light components transmittedthrough the respective interference filters 31–39 by means of photomultipliers 51–59 as photodetecting means examples in place of thephotodiodes 41–49. As in the case of light components to composefluorescence, when the intensity is extremely small, since it isdifficult to detect the light components by the photodiodes 41–49, thelight components are detected by the photo multipliers 51–59. Herein,the reason why the traveling direction of light L from a light source 3is changed by 90 degrees at a sample cell S is to prevent the light Lfrom the light source 13 from being directly made incident into aspectroscopic portion 13. Thereby, reliability in detecting respectivelight components is improved. Herein, the spectroscopic instrument 2also has similar effects to those of the spectroscopic instrument 1.

According to the spectroscopic instruments 1 and 2, light components ofnine wavelength types are detected by providing nine interferencefilters, which allows light components of different wavelengths totransmit. However, the number of multiple wavelengths detected by aspectroscopic instrument of the present invention is not limited hereto,but the number of multiple wavelengths can be arbitrarily set bychanging the number of interference filters to allow light components ofdifferent wavelengths to transmit.

In addition, the spectroscopic instruments 1 and 2 cause the lens 11 tomake light emitted from the sample cell S into parallel light by a lens11 and make the same incident into the interference filter, however,when absorption of the interference filter at a specific wavelength isgreat or when intensity of light emitted from a light source or a sampleis small at a specific wavelength, efficient spectroscopy is madepossible by focusing on that filter. For example, in the presentembodiment, improvement in the detecting light amount is made possibleby focusing on the 340 nm interference filter 31, and a difference inthe light intensity detected by another interference filter can be madesmall.

In the spectroscopic instrument according to the present invention, aplurality of interference filters split their respective incident lightsinto a light component to be reflected and a light component to betransmitted, the reflected light component is made into an incidentlight into an interference filter positioned in the next order, andlight from the light source is transmitted to the plurality ofinterference filters in order, whereby multiple wavelengths aredetected. According to the present inventor, it has been discovered thatdielectric layers to compose an interference filter have relativelysatisfactory features to reflect a light component of wavelengths otherthan a light component of a wavelength transmitted through theinterference filter. Accordingly, an incident light of a relatively highintensity is made into interference filters positioned in the latterorder as well, and multiple wavelengths can be detected at a highdetecting efficiency.

In addition, according to the spectroscopic instrument according to thepresent invention, an incident light into the respective interferencefilters are split into a light component to be transmitted and a lightcomponent to be reflected, and the reflected light component is madeinto an incident light into an interference filter positioned in thenext order, therefore, speedy detection of multiple wavelengths becomespossible.

According to a spectroscopic method of the present invention, it becomespossible to detect multiple wavelengths at a high detecting frequencyand at a high speed.

Moreover, the spectroscopic instrument according to the aforementionedembodiment comprises a plurality of photodetectors arranged so that theabove-described light is made incident in time series at the speed oflight, and the above-described photodetectors each have a photoelectrictransducer and an interference filter fixed to the light incident sideof the photoelectric transducer, a transmitting wavelength and areflecting wavelength band of the respective interference filters aredifferent, and a transmitting wavelength of the interference filter of alatter order is included in a reflecting wavelength band of theinterference filter of a former order.

Herein, irrespective of the transmitting wavelength of the interferencefilter, a total reflection mirror having an aperture may be provided onthe light incident surface side thereof.

In addition, if the plurality of photodetectors are arranged in acircle, an air flow-in path into the inside of the circle becomesnarrow, therefore, an output fluctuation of the photodetectors caused byair undulations can be suppressed.

In addition, if an infrared cut filter is arranged on the near side ofthe photodetectors, generation of noise caused by infrared light can besuppressed, and if the inner surface of a cylindrical body to compose aphotodetector is black, noise caused by an internal reflection of thecylindrical body can be suppressed.

Hereinafter, description will be given in detail.

FIG. 6 is a plan view of a spectroscopic instrument according to anotherembodiment. This spectroscopic instrument comprises, similar to theaforementioned spectroscopic instrument, a plurality of photodetectorsD1–D22. Herein, focusing on the first-order photodetector D1, this isreferred to as a first photodetector, and the next-order photodetectorD2 is referred to as a second photodetector. Since components of theplurality of photodetectors D1–D22 are identical except for interferencefilter characteristics, herein, a description will be given of thephotodetector D1 as a representative.

FIG. 7 is a sectional view of a first photodetector D1 when the firstphotodetector D1 is cut along the optical axis of the firstphotodetector D1.

The photodetector D1 has a first photodiode (a first photoelectrictransducer) PD1 and a first interference filter DF1 fixed to the lightincident side of the first photodiode PD1. The first interference filterDF1 has a disk shape, and its side circumferential surface is in contactagainst the inner surface of a cylindrical body CY1 and is fitted in theinside of this cylindrical body CY1, and the cylindrical body CY forms aholder. Namely, the first cylindrical body CY1 accommodates the firstphotodiode PD1 and has an opening, and the opening of the firstcylindrical body CY1 is blocked by the first interference filter PD1.

The light incident surface side of the cylindrical body CY1 is bentinward, and against this bent portion CY′, the circumference of thelight incident surface of the first interference filter DF1 is incontact, whereby the first interference filter DF1 is positioned in theoptical axis direction. To the light emitting surface of the firstinterference filter DF1, the first photodiode PD1 is attached. Thecylindrical body CY1 accommodates the first interference filter DF1 andfirst photodiode PD1, wherein its inner surface has received anon-reflective treatment. Namely, the inner surface of the cylindricalbody CY1 has been painted black. Namely, the color of the inner wall ofthe cylindrical body CY1 is black, thereby unnecessary reflection issuppressed to carry out accurate detection.

Herein, an n-th order photodetector is a conversion of the firstphotodetector D1 into an n-th photodetector, and in a case of the secondphotodetector D2, this second photodetector D2 has a second photodiode(second photoelectric transducer (PD2)) and a second interference filter(DF2) fixed to the light incident side of the second photodiode (PD2).

Now, FIG. 6 will be referred to again.

The second photodetector D2 is arranged so that a reflected light fromthe first interference filter DF1 is made incident, and a transmittingwavelength (λ_(T1)) of the first interference filter DF1 is differentfrom a reflecting wavelength band (Δλ_(R1)) of the same, and atransmitting wavelength (λ_(T2)) of the second interference filter (DF2)is included in the reflecting wavelength band (Δλ_(R1)) of the firstinterference filter DF1.

The third photodetector D3 is arranged so that a reflected light fromthe second interference filter (DF2) is made incident, and has a thirdphotodiode (PD3) and a third interference filter (DF3) fixed to thelight incident side of the third photodiode (PD3). A transmittingwavelength (λ_(T2)) of the second interference filter (DF2) is differentfrom a reflecting wavelength band (Δλ_(R2)) of the same, and atransmitting wavelength (λ_(T3)) of the third interference filter (DF3)is included in the reflecting wavelength band (Δλ_(R2)) of the secondinterference filter.

By use of “n”, which is an integer equal to 1 or more, this relationshipcan be expressed as follows. Namely, an n+1-th photodetector (Dn+1) isarranged so that a reflected light from an n-th interference filter(DFn) is made incident, and a transmitting wavelength (λ_(Tn)) of then-th interference filter (DFn) is different from a reflecting wavelengthband (Δλ_(Rn)) of the same, and a transmitting wavelength (λ_(Tn+1)) ofthe n+1-th interference filter (DFn+1) is included in the reflectingwavelength band (Δλ_(Rn)) of the n-th interference filter (DFn).

A light made incident into a spectroscopic instrument is made incidentwith an incident angle θ into the photodetector D1, a light reflected bythe photodetector D1 is made incident with an incident angle θ into thenext-order photodetector D2, and a light reflected by the photodetectorD2 is further made incident with an incident angle θ into the next-orderphotodetector D3. Namely, the incident angle θ of light into the firstinterference filter is greater than 0° and not more than 10°, and theincident angle θ of the light into the second interference filter (DF2)is greater than 0° and not more than 10°. In the present example,θ=7.50°. This is because, if the incident angle θ exceeds 10°,transmittance of a wavelength made incident into the interference filteris deteriorated and a wavelength shift occurs.

Focusing on the first, second, and third photodetectors D1, D2, and D3,the first, second, and third photodetectors D1, D2, and D3 are arrangedso that normal lines to the light incident surfaces of the first,second, and third interference filters DF1, (DF2), and (DF3) intersectat one point Q. By arranging the respective photodetectors as such, thephotodetectors gradually form a circle, and the circular internal spaceis gradually closed to the outside, therefore, influences of dust andundulations of outside air can be suppressed to carry out accuratedetection.

Namely, this spectroscopic instrument comprises a plurality ofphotodetectors Dn (n is an integer equal to 1 or more) arranged so thata light is made incident in time series at the speed of light, and thephotodetectors Dn each have a photodiode PDn and an interference filterDFn fixed to the light incident side of the photodiode PDn, atransmitting wavelength λ_(Tn) and a reflecting wavelength band Δλ_(Rn)of each interference filters DFn are different, and a transmittingwavelength λ_(Tn+1) of a latter-order interference filter DFn+1 isincluded in a reflecting wavelength band Δλ_(Rn) of the former-orderinterference filter DFn, Moreover, these photodetectors D1–D23 arearranged in a circular shape, and accurate detection can be carried out.Herein, in order to form a circle, the photodetectors D1–D23 arearranged so that normal lines to the light incident surfaces of therespective photodetectors D1–D23 pass through one point. Although 23photodetectors have been arranged in the present example, as a matter ofcourse, this quantity is appropriately determined according to thenumber of wavelengths for which spectroscopy is demanded. In addition,when the quantity of photodetectors is small, shading materials arearranged in place of photodetectors.

In the present example, although the photodetectors D1–D23 have beenmade identical except for the interference filter construction, a totalreflection mirror having an aperture may be provided on the lightincident surface side of the interference filter. Although allphotodetectors D1–D23 may be replaced by such mirror-typephotodetectors, for example, only the photodetectors D15–D23 on thelatter-order side where light intensity becomes relatively weak may bereplaced by total reflection mirror-type photodetectors. Herein, adescription will be given on the premise that, as a representativephotodetector, the first photodetector D1 is a total reflectionmirror-type photodetector.

FIG. 8 is a sectional view of a first photodetector D1 when a totalreflection mirror-type first photodetector D1 is cut along the opticalaxis of the first photodetector D1.

FIG. 9 is a view of a photodetector D1 showing internal components of aphotodetector D1 in an exploded manner.

The difference from the photodetector D1 shown in FIG. 6 is in that atotal reflection mirror M1 is provided on the light incident surfaceside of the interference filter DF1 and a holder bent portion CY′ is incontact against the outer circumferential portion of the light incidentsurface of the total reflection mirror M1. Other aspects of theconstruction are identical to those shown in FIG. 6.

Namely, in this spectroscopic instrument, to the light incident surfaceof the first interference filter DF1, attached is a total reflectionmirror M1 having an aperture AP1.

The total reflection mirror M1 is composed of a glass plate g1 and ametal reflecting film m1 formed on the glass plate g1. The metalreflecting film m1 is made of aluminum and has an aperture AP1 for alight incidence. Although the metal reflecting film m1 can be formed onthe glass plate g1 by a vapor deposition method, it may also be formedby a wet plating method. The glass plate g1 is formed on the lightincident surface of the interference filter DF1.

A specific wavelength component λ_(T1) of light made incident into theaperture AP1 of the metal reflecting film m1 is transmitted through theglass plate g and interference filter DF1 and reaches the light incidentsurface of the photodiode PD1, that is, a photodetecting region. In thephotodetecting region, a photoelectric conversion is carried out and anelectric signal of a signal intensity according to the incident lightintensity is outputted from the photodiode PD1.

A wavelength band Δλ_(R1) of light incident onto the metal reflectingfilm ml is reflected and reaches the following-order photodetector D2.

Namely, the present spectroscopic instrument comprises a plurality ofphotodetectors D1–D23 arranged so that a light is made incident in timeseries at the speed of light, and when a description is given of thephotodetector D1 as are presentative of the photodetectors D1–D23(D15–D23), this photodetector D1 has a photodiode PD1, an interferencefilter DF1 fixed to the light incident side of the photodiode PD1, and atotal reflection mirror M1 having an aperture AP1 fixed to the lightincident side of the interference filter DF1.

In this case, a light having an intensity of an order that thephotodetector D1 can detect passes through the inside of the apertureAP1, and by effectively reflecting the remaining light by the totalreflection mirror M1, a deterioration in detection sensitivity can besuppressed in the latter-order detectors.

Such a total reflection mirror-type photodetector D1 can also be appliedto the spectroscopic instrument as shown in FIG. 1, as well.

FIG. 10 is a view showing an example where, in the spectroscopicinstrument shown in FIG. 1, total reflection mirror-type photodetectorsD1–D5 . . . have been applied. The photodetectors D1, D3, D5 . . . ofthe odd-numbered orders are lined up in a row to form a firstphotodetector array, the photodetectors D2, D4, . . . of theeven-numbered orders are lined up in a row to form a secondphotodetector array. The first and second photodetector arrays areopposed to each other. In the present example, a position of conversionby the lens 11 has been set on the second photodetector D2, the lightbecomes more divergent as the position shifts toward the latter-orderside beyond the position of conversion. This light can be made into aparallel light so that divergence hardly occurs. The aforementionedaperture diameter may be enlarged on the latter-order side beyond theposition of conversion to meet light divergence. Moreover, the aperturediameters can be identical.

FIG. 11 is an enlarged sectional view of the third photodetector D3shown in FIG. 10. Although the structure of the third detector D3 isidentical to that of the first detector D1 except for characteristics ofthe interference filter DF3, the third detector D3 comprises, in orderfrom the light incident side, a total reflection mirror M3 composed of ametal reflecting film m3 and a glass plate g3, a third interferencefilter DF3, and a photodiode PD3, and these are accommodated in acylindrical body CY3. The front end portion of the cylindrical body CY3is bent inward, and the inner surface of the bent portion CY3′ is incontact against the outer circumferential portion of the totalreflection mirror M3. A wavelength component λ_(T3) of light transmittedthrough an aperture AP3 of the total reflection mirror M3 reaches thephotodiode PD3, and a wavelength band Δλ_(R3) of light incident onto themetal reflecting film m3 is reflected.

Herein, as shown in FIG. 12, the spectroscopic instrument may furthercomprise an infrared cut filter arranged on the path of an incidentlight into the first interference filter DF1.

Thereby, depending on the interference filter, even if it has acharacteristic to transmit an infrared-region wavelength, detection ofthis component as noise can be prevented.

Moreover, as shown in FIG. 13, the spectroscopic instrument may furthercomprise an infrared cut filter arranged on the path of an incidentlight into the second interference filter DF2.

Moreover, although the aforementioned photoelectric transducer PDn was aphotodiode, this may be a photo multiplier.

Industrial Applicability

The present invention can be utilized for a spectroscopic instrument anda spectroscopic method used in a blood test, for example.

1. A spectroscopic instrument for detecting a plurality of lightcomponents different in wavelengths, comprising: a plurality ofinterference filters which are respectively different in wavelengths oflight components to be transmitted therethrough and to which a lightfrom a light source is transmitted in order and a plurality ofphotodetecting means corresponding to each of said plurality ofinterference filters, for detecting a light component transmittedthrough the corresponding interference filter, wherein each of saidplurality of interference filters splits an incident light into a lightcomponent to be reflected and a light component to be transmitted andmakes the reflected light component into an incident light into aninterference filter positioned in the next order, whereby the light fromsaid light source is transmitted to said plurality of interferencefilters in order, an incident angle of light into each of saidinterference filters is greater than 0° and not more than 10°.
 2. Aspectroscopic method for detecting a plurality of light componentsdifferent in wavelengths, in which: at each of a plurality ofinterference filters respectively different in wavelengths of lightcomponents to be transmitted therethrough, an incident light into eachinterference filter is split into a light component to be reflected anda light component to be transmitted and the reflected light component ismade into an incident light into an interference filter positioned inthe next order, whereby a light from a light source is transmitted tosaid plurality of interference filters in order so as to detect lightcomponents transmitted through the respective interference filters, anincident angle of light into each of said interference filters isgreater than 0° and not more than 10°.
 3. A spectroscopic instrumentcomprising: a first photodetector having a first photoelectrictransducer and a first interference filter fixed to the light incidentside of said first photoelectric transducer and a second photodetectorarranged so that a reflected light from said first interference filteris made incident, having a second photoelectric transducer and a secondinterference filter fixed to the light incident side of said secondphotoelectric transducer, wherein a transmitting wavelength of saidfirst interference filter is different from a reflecting wavelength bandof the same, and a transmitting wavelength of said second interferencefilter is included in the reflecting wavelength band of said firstinterference filter, an incident angle of light into said firstinterference filter is greater than 0° and not more than 10°, and anincident angle of light into said second interference filter is greaterthan 0° and not more than 10°.
 4. The spectroscopic instrument as setforth in claim 3, further comprising: a third photodetector arranged sothat a reflected light from said second interference filter is madeincident, having a third photoelectric transducer and a thirdinterference filter fixed to the light incident side of said thirdphotoelectric transducer, wherein a transmitting wavelength of saidsecond interference filter is different from a reflecting wavelengthband of the same, and a transmitting wavelength of said thirdinterference filter is included in the reflecting wavelength band ofsaid second interference filter.
 5. The spectroscopic instrument as setforth in claim 4, wherein said first, second, and third photodetectorsare arranged so that normal lines to the light incident surfaces of saidfirst, second, and third interference filters intersect at one point. 6.The spectroscopic instrument as set forth in claim 3, furthercomprising: an infrared cut filter arranged on the path of an incidentlight into said first interference filter.
 7. A spectroscopic instrumentcomprising: a first photodetector having a first photoelectrictransducer and a first interference filter fixed to the light incidentside of said first photoelectric transducer and a second photodetectorarranged so that a reflected light from said first interference filteris made incident, having a second photoelectric transducer and a secondinterference filter fixed to the light incident side of said secondphotoelectric transducer, wherein a transmitting wavelength of saidfirst interference filter is different from a reflecting wavelength bandof the same, and a transmitting wavelength of said second interferencefilter is included in the reflecting wavelength band of said firstinterference filter, wherein a total reflection mirror having anaperture is attached to the light incident surface of said firstinterference filter.
 8. The spectroscopic instrument as set forth inclaim 3, comprising: a first cylindrical body which accommodates saidfirst photoelectric transducer and has an opening, wherein the openingof the first cylindrical body is blocked by said first interferencefilter.
 9. The spectroscopic instrument as set forth in claim 8, whereinthe color of the inner wall of said first cylindrical body is black. 10.A spectroscopic instrument comprising: a plurality of photodetectorsarranged so that said light is made incident in time series at the speedof light, wherein said photodetectors each have a photoelectrictransducer and an interference filter fixed to the light incident sideof the photoelectric transducer, a transmitting wavelength and areflecting wavelength band of the respective interference filters aredifferent, and a transmitting wavelength of said interference filter ofa latter order is included in a reflecting wavelength band of saidinterference filter of a former order, an incident angle of light intosaid first interference filter is greater than 0° and not more than 10°,and an incident angle of light into said second interference filter isgreater than 0° and not more than 10°.
 11. The spectroscopic instrumentas set forth in claim 10, wherein said plurality of photodetectors arearranged in a circular shape.
 12. The spectroscopic instrument as setforth in claim 11, wherein said photodetectors are arranged so thatnormal lines to the light incident surfaces of said respectivephotodetectors pass through one point.
 13. A spectroscopic instrumentcomprising: a plurality of photodetectors arranged so that said light ismade incident in time series at the speed of light, wherein saidphotodetectors each have a photoelectric transducer, an interferencefilter fixed to the light incident side of said photoelectrictransducer, and a total reflection mirror having an aperture fixed tothe light incident side of said interference filter.
 14. Thespectroscopic instrument as set forth in any one of claims 3 through 13,wherein said photoelectric transducer is a photodiode or a photomultiplier.
 15. The spectroscopic instrument as set forth in any one ofclaims 1 through 13, further comprising holders, each of said holdersaccommodating each of said interference filters and each of saidphotoelectric transducers.
 16. The spectroscopic instrument as set forthin any one of claims 1 through 13, further comprising a holding portion,said holding portion holding all of said interference filters.
 17. Thespectroscopic instrument as set forth in any one of claims 1 through 13,further comprising a casing for accommodating all of saidphotodetectors.
 18. The spectroscopic instruction as set forth in anyone of claims 1 through 13, further comprising a lens for entering lightto one of said interference filters, said lens focusing light on thisinterference filter.